The invention relates generally to roll control spoilers for aircraft and more particularly to a novel spoiler control system.
It is well known to those versed in the art of applied aerodynamics that spoilers constitute an effective and efficient means for altering the aerodynamic characteristics of a wing, particularly as an effective means for providing control of an aircraft about its longitudinal or rolling axis. It is common in the art to provide movable trailing edge flaps on the wings of airplanes for the purpose of producing a higher coefficient of lift than the wing could produce without the use of flaps. Furthermore, it is known that it is advantageous to have the flaps extend across as much of the lateral span of the wing as possible considering all requirements other than high coefficients of lift. One such requirement is the necessity for effective roll control, most commonly provided by ailerons.
The use of spoilers in place of ailerons for roll control is well known. As is also well recognized, the aerodynamic loading on the active or up spoiler tends to displace the spoiler "up" which causes a decentering moment on the control wheel. Thus, the problem becomes in manually powered spoiler roll control systems to counteract the decentering moments in order to obtain satisfactory cockpit control characteristics. Further recognized of course, is the fact that the decentering moment from the upwardly-moving spoiler into the control system increases as the wing flaps are deployed downwardly. As the flaps extend to full down position the decentering moment also increases to its maximum. Stated another way, spoiler control has a much larger decentering moment to contend with when the flaps are down than when the flaps are retracted.
Various solutions to counteract the decentering moment on the spoilers have been tried. Springs have been employed in control systems but they have disadvantages if they are the only means in the system. So-called "Q" springs are used in many forms but they have not proved to be satisfactory in contributing to proper cockpit control feel. One approach in the prior art has been to use spoilers with the flaps out but, upon retraction of the flaps, these spoilers become a fixed part of the wing because ailerons are incorporated in the back of the flap. In other words, roll control is provided by the ailerons with the flaps up and by spoilers or a combination of spoilers and ailerons with the flaps down. Another aircraft manufacturer has a set relationship of active spoiler motion to inactive spoiler motion in response to control wheel movement. This constant schedule of up and down spoiler movement with respect to each other pertains regardless of whether the wing flaps are retracted or extended. Large commercial and military aircraft have used power spoiler control systems, but no manual spoiler control systems are known which generate a different schedule of control inputs with flaps extended.
The only known patent which is related is U.S. Pat. No. 3,184,186.